1. Field of the Invention
This invention relates to a so called magnestylus system recording display device which record and display images by attaching a magnetic electroconductive developer onto an image holding member by electrical adsorption force.
2. Related Background Art
In the prior art as the recording display device which enables highly precise and large picture face display simply and inexpensively, there has been proposed the so called magnestylus system (see, for example, Japanese Patent Publication No. 51-46707). Its principle is, as shown in FIG. 5 thereof, to rotate a columnar magnet 2 within a nonmagnetic cylinder 3, convey a colored magnetic electroconductive developer 1 through its magnetic force on the nonmagnetic cylinder 3 and feed the toner onto the needle-like recording electrodes 4 arranged densely along the axis direction on the nonmagnetic cylinder 3.
And, a voltage is applied according to image information between the electroconductive layer 7 of an image holding member 5 comprising a recording layer 6 on the surface side and an electroconductive layer 7 on the backside nd the recording electrodes 4, to form an image by attaching the magnetic developer 1 onto the image holding member 5 only at the portion where voltage is applied.
However, in the case of the prior art as described above, performances with respect to high contrast, high life, stability under various environments, high reliability, etc. have been unsatisfactory.
Accordingly, as the method for enhancing the contrast of the image holding member 5, various methods as shown below have been considered:
(1) a method in which diffusion reflection is effected by making the light reflecting surface uneven;
(2) a method in which an anodically oxidized film of aluminum is used (see Japanese Patent Publication No. 51-46707);
(3) a method in which a diffusion reflection layer having fine particles dispersed in a binder resin is laminated on an electroconductive layer 7;
(4) a method in which a diffusion reflection layer having fine particles dispersed in a binder resin and further a dielectric layer are laminated on an electroconductive layer 7.
However, according to the method of (1), the magnetic electroconductive developer is trapped at the concavities to bring about lowering in contrast.
According to the method of (2), cracks will be generated during anodic oxidatiOn, whereby voltage leak is liable to occur. Also, the surface becomes uneven to give rise to similar troubles as in the method of (1). Further, whiteness of the anodically oxidized film is low to make no sufficient contrast. Further, when there is a change in environment, voltage leak will frequently occur, whereby various problems will emerge such that the density of recording or display is lowered, failing to make sufficient contrast.
On the other hand, according to the method of (3), although the whiteness at the initial stage is excellent in contrast, the magnetic electroconductive developer is trapped during repeated uses by the fine voids generated by dispersing fine particles to bring about lowering in contrast.
Also, adsorption and desorption of water are marked at the fine void portions remaining when the temperature, the humidity, etc. change, whereby electrical resistance will be greatly changed. For this reason, the electrical adsorption force of the developer changes depending on the environment, whereby there ensues the problem that the change in contrast of image is great. In other works, under highly humid conditions, as the result of adsorption of humidity which progresses remarkably through fine gaps, the electrical resistance is greatly lowered to make the adsorption force of the magnetic electroconductive developer, resulting in lowering of contrast.
According to the method of (4), although whiteness at the initial stage is high and the environmental stability is excellent, whiteness still tends to be lowered slightly during repeated uses.